This invention relates to an improved refrigeration system for chilling a circulating water supply for reuse in cooling industrial equipment, and particularly to the thermal exchanger of such a system.
Water chillers are useful for chilling a circulating water supply for reuse in the cooling of industrial equipment. The uses for such equipment are many including typical applications such as injection blow molding, extruding, printing and etching, controlled chemical processing, controlled food processing, and industrial machine cooling. It has been found, for instance, that use of a water chiller with many industrial machines, such as hydraulic presses, compressors, metal treating ovens, and special metal fabrication processes results in definite improvements in operating efficiency. The advantages of using such equipment have been readily apparent to those skilled in the art even though such equipment has previously not been fully developed to the desired extent. With the water chillers heretofore available, it has been necessary to utilize complex refrigeration equipment of large capacity using significant amounts of energy even then oftentimes failing to achieve a fully satisfactory temperature drop in the circulating water supply.
With respect to most prior water chillers, the refrigeration systems have usually been conventional designs of types commonly available for many years. The coiled refrigerant tubes or evaporators are simply emersed in a container of water to chill the water used to cool the equipment. It is significant to note that such systems continuously introduce or mix hot water coming from the equipment to be chilled with partially chilled water being withdrawn for recirculation to the equipment. The coiled refrigerant tubes or evaporators are therefore impeded in achieving the desired temperature drop in the water by reason of the constant intermixing of hot water with the partially chilled water.
U.S. Pat. Nos. 3,435,627, 3,310,103, and 3,180,108 disclose systems representing prior attempts to overcome some of such problems. Other patents reflecting the state of the art are U.S. Pat. Nos. 2,762,209, 2,511,582, 2,471,137, and 3,280,592.
In the aforementioned co-pending application, a system is disclosed wherein two or more thermal exhange assemblies are disposed within a container below the normal water level thereof, each assembly including a coiled refrigerant tube and a coiled water tube coaxially disposed therein, the flow through the water tube being in a direction opposite to the flow of refrigerant, and the water outlet of one assembly being connected to the water inlet of the next assembly to dispose the water circuits of the two assemblies in series relation. Water cooled by the assembly of the final stage is discharged directly into the container. Such application also discloses other features, including the provision of separate expansion valves for each of the thermal exchange assemblies.
In the system of the present invention, the thermal exchanges each comprise three tubes. A coiled refrigerant tube has a coaxial water tube of substantially smaller diameter extending therethrough, the two tubes being arranged so that refrigerant and water flow in opposite directions. The outlet for the coaxial water tube is connected to the inlet of a helical second water tube which is wound about the outside of the refrigerant tube, thus carrying chilled water in a helical passage and in a reverse direction along the outside of the refrigerant tube. It has been found that such a relationship promotes greater cooling efficiency and results in a highly effective water cooling system.
In the embodiment disclosed, each thermal exchange assembly discharges cold water from its helical water tube directly into the enclosure which forms the water container; hence, such assemblies operate in parallel rather than in series. It has been found that the high cooling efficiency of such thermal exchange assemblies makes parallel operation particularly suitable; however, a series arrangement might be utilized, with the outlet of a helical water tube of one assembly discharging into the inlet of the coaxial water tube of the next assembly, if cooling to extremely low temperatures is required.
Other objects, features, and advantages of the invention will appear from the specification and drawings.